In this kind of conveyor chain for the travel way, there has been a conveyor belt formed by a number of plastic chain modules or links having a plurality of ribs. The links are connected to each other by connecting pins as shown, for example, in Japanese Laid-Open Patent Publication No. 2006-111449 (page 1, FIG. 1).
However, since in such a conveyor belt protrusions are protruded upwardly from a transfer surface, when wheels of a work carrier or the like are grounded and rolled on the exposed transfer surface, the traveling vibration and traveling resistance are large. Thus there is a problem that an excessive traveling load is created by the upwardly-projecting protrusions.
Further, when a gap between chain modules in the pitch direction is reduced to provide a transfer surface of high density, a belt inner circumferential side back bend radius cannot be decreased because of a contact interference between adjacent projecting protrusions of the modules. To avoid the interference, an intermediate idler or the like must be appropriately disposed, and there is a problem, in that it is difficult to ensure a suitable belt slack on the belt return run.